1. Field of the Invention
The present invention relates to a sensor unit and a magnetic flux concentrating module including the sensor unit.
2. Description of the Related Art
Many vehicles include an electric power steering (EPS) system. The EPS system is driven at a time when a steering wheel is operated. Thus, the EPS system has advantages, such as improvement of fuel efficiency, compared with a hydraulic power steering system.
In the EPS system, a torque detecting device is used for detecting a torque generated due to a steering operation by a driver as described, for example, in Japanese Patent No. 4,046,049.
The torque detecting device includes, for example, a multipolar magnet, a yoke, and a magnetic flux concentrating ring. In the multipolar magnet, an N pole and an S pole are alternately arranged on a cylindrical surface. The yoke is disposed at a periphery of the multipolar magnet. The magnetic flux concentrating ring is disposed at a periphery of the yoke.
The magnetic flux concentrating ring concentrates magnetic flux through teeth of the yoke disposed at the periphery of the multipolar magnet. At an end portion of the magnetic flux concentrating ring, protruding parts protrudes radially outward. The protruding parts have a clearance therebetween in a vertical direction. Between the protruding parts, a Hall IC is disposed. The torque detecting device detects a change in the torque as a change in magnetic flux passing through the Hall IC.
In the conventional art, components including the Hall IC are welded to a bus bar that is called a terminal. Specifically, the bus bar is bent into an L-shape by press working. The Hall IC is treated with projection welding. After a capacitor is soldered and an epoxy molding is performed, a harness is treated with resistance welding. Then, a hot melt molding is performed in such a manner that stress does not concentrate at a welding portion of the harness, and thereby a sensor unit including the Hall IC is formed. The above-described process is performed so as to improve a detection accuracy of the Hall IC.
However, the above-described process requires a long time. Furthermore, because the bus bar bent into the L-shape is used and the Hall IC protrudes from the bus bar, a dimension of the sensor unit is large.